The present invention relates to a supply circuit or a power supply unit for supplying electronic devices with current or voltage, having a rectifier circuit and a transformer, the primary winding of which is connected with the inputs of the supply circuit and the secondary winding of which is connected with the rectifier circuit. The supply circuit or power supply unit has at least one high-capacity capacitor connected on the output side of the rectifier circuit for the smoothing of the generated direct current or the generated direct voltage.
Supply circuits of the above type are required in large numbers in order to be able to supply electronic equipment via the public electricity supply network. According to the Swiss Patent Document CH-PS 621 216 which illustrates a circuit of this type, these circuits are always constructed of discrete elements. In this known circuit, the elements may be arranged on printed circuit boards which generally also carry the elements or integrated circuits of the electronic device to be supplied. This means that the supply circuit must generally be constructed together with the electronic device. This leads to relatively high manufacturing expenditures for the electronic device.
Although supply circuits may be used whose discrete elements, together with a transformer, are mounted on a separate printed circuit board and are cast together to form a block, this construction has the disadvantage that it requires a lot of space. Compact and completely prefabricated supply circuits or power supply units for different electronic devices so far have not been developed, despite an existing demand.
The U.S. Pat. No. 3,541,433 shows a power circuit at which, on the output side, high currents (of, for example, 200 A) can be tapped at a low voltage, for example, 3 V. This circuit essentially shows a transformer arrangement and semiconductor elements, in which the winding bodies of the transformer windings also carry the semiconductor elements and are provided with cooling ribs for the carrying away of considerable amounts of heat which are generated by the semiconductor elements because of the high current intensities.
The German Patent Documents DE-PS 34 28 210 and the DE-PS 27 06 560 each show completely prefabricated high-voltage cascades which essentially comprise semiconductor rectifier elements or diodes and capacitors.
From the German Patent Document DE-OS 31 25 281, an R-C element is known which has a ceramic multi-layer capacitor as well as a resistance path arranged on a cover surface of the multi-layer capacitor. In this case, the element is designed such that an R-C series connection as well as an R-C parallel connection can be established.
The German Patent Document DE-PS 459 705 also illustrates an R-C element which, as an R-C parallel connection, is composed of discrete elements.
From the German Design Documents 71 31 688 and 17 96 813, it is known to develop wound capacitors in a ring shape in such a manner that other elements, such as an electric motor, a battery or semiconductor elements, such as rectifiers or the like, can be arranged inside the cylinder space. In this manner, power supply units for flash light equipment and the like can be produced that are relatively compact and are wrapped by the capacitor.
The U.S. Pat. Document US-PS 47 94 510 shows a rectifier which is constructed to be compact and to withstand high mechanical stress in such a manner that it can be housed on or in the rotor of an electric motor or of a generator.
It is an object of the present invention to provide a compact supply circuit which can be completely prefabricated and is suitable for a large number of electronic devices.
This and other objects are achieved by the present invention which provides a supply circuit for supplying electronic devices with current or voltage and is mountable as a module, the supply circuit comprising input and output connections, a rectifier circuit, a transformer having a primary winding coupled with the inputs of the supply circuit and a secondary winding coupled with the rectifier circuit and at least one high-capacity capacitor. The capacitor is coupled with an output of the rectifier circuit for smoothing generated direct current or direct voltage. The capacitor has a housing which houses the capacitor, the rectifier circuit and the transformer in or on the housing. The input and output connections are arranged on the housing so as to be accessible from outside of the housing. At least a part of the housing consists of a magnetizable material and carries the primary and secondary windings in the manner of a winding body.
The present invention utilizes the recognition that supply circuits of the earlier-described type each have at least one high-capacity capacitor and a correspondingly large housing which must be enlarged only slightly in order to arrange in it or on it the other parts of the supply circuit. Thus a supply module can be created with a particularly low space requirement.
According to the present invention, particularly little space is required also for the transformer because the housing of the high-capacity capacitor which is made of a magnetizable material or a magnetizable housing part is used as the winding and supporting body for the transformer windings. The housing therefore has a double function in that it is used as a winding and supporting body for the transformer windings as well as a wrapping for the capacitor.
Although on the basis of this construction according to the invention, the efficiency of the transformer may be slightly lower than that of a conventional discrete transformer, this results in no serious disadvantage because the possible impairment of the efficiency is more than compensated by the particularly compact construction permitted in the invention. At the same time, the design according to the present invention takes the fact into account that the power requirement of most electronic devices is so low that a good efficiency of the supply circuit is negligible. It should be noted that, by means of the transformer, a galvanic separation is ensured between the inputs of the supply circuit which are generally connected to the public electricity network, and its outputs which are connected with the respective device to be supplied which is often sensitive.
In addition, an annulus may be arranged on the housing for receiving the primary and secondary windings of the input transformer, this annulus having at least one annular wall area made of a magnetizable material. In this case, a particularly high efficiency of the transformer is reached if the annulus is completely enclosed with a magnetizable material. The housing parts forming the annulus may be constructed as parts that are separate from the capacitor housing.
In an embodiment constructed according to the present invention, heat-conducting elements of the supply circuit, such as rectifier diodes and voltage regulators, are arranged in a heat-conducting contact with the housing in order to carry off the forming heat. Thus, the housing may also have a cooling function. If necessary, cooling ribs may be arranged on the housing in order to improve the removal of heat.
In an embodiment of the present invention, the input as well as the output connections of the supply circuit are constructed as holding elements in order to be able to house the module formed by the supply circuit according to the invention more easily in the device to be supplied.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.